A fitting system of this type is known from WO 2011/160771 A1. A special return spring holds the stop module in an abutment position with respect to the fitting. The return spring has a first and a second spring end, which both, as seen in the radial direction, do not project beyond the outer contour of the stop module, and therefore the spring ends are not visible during the installation of the stop module on the fitting. This makes it difficult to insert the first spring end into a holder of the fitting. The second spring end is hooked into one of eight holes. Due to the plurality of holes, the second spring end may be inadvertently hooked into a hole not provided therefor. In addition, the insertion of the second spring end in one of the holes requires precise positioning of the second spring end over the corresponding hole.
DE 10 2012 006 227 A1 discloses a fitting system for a vehicle seat, which fitting system comprises two stop modules. A first stop module is integrally formed on a first operating element which is fitted on a left outer side of the seat. A second stop module is integrally formed on a second operating element which is fitted on a right outer side of the seat. The first operating element and the second operating element significantly differ in shape from each other, and therefore it is not possible for transpositions to occur when installing the operating elements on the vehicle seat.
WO 2005 016 685 A1 discloses a fitting for a vehicle seat, in particular for a motor vehicle seat, with a first fitting part, a second fitting part which is rotatable relative thereto and is lockable, and a profiled shaft, the actuation of which unlocks the fitting, wherein a spring pretensions the shaft counter to the actuating direction and the spring at the same time secures the shaft in relation to the fitting in the axial direction of the shaft.